One evening in the late autumn of 1997, Jeff and Lori Leibovitz arrived at Skiles Test Elementary School in Indianapolis for a meeting with their son Adam's first-grade teacher. The Leibovitzes were upbeat. First-grade conferences are typically full of wonderful reports about children's wonderful progress in learning to read and write. But the Leibovitzes walked into Adam's classroom that night to find the assistant principal sitting with Adam's teacher. The assistant principal did most of the talking. She told them their son showed classic signs of attention deficit hyperactivity disorder, or ADHD: He had trouble sitting still in class; his focus pinballed around the room; his hands were a whirl of perpetual motion. Adam's teacher had taken to giving him rubber bands to occupy his busy fingers.

Jeff and Lori listened in shock. Adam was a rambunctious kid, but his behavior didn't strike them as unusual. Adam's ADHD wasn't extreme or debilitating, the assistant principal told the Leibovitzes. But that wasn't necessarily a good thing. The boy's condition was acute enough to cause learning problems but mild enough that he'd likely slip through the system's safety net for special-needs students.

"It was a horror story," Lori recalls. "Here was our oldest child, just starting school, and we're told that he's always going to struggle with this. They said he'd fall through the cracks and would never amount to anything. It was earthshaking."

At the time, ADHD diagnoses were exploding across the United States. From 1990 to 1998 the number of children and adults identified as having the disorder shot up from 900,000 to nearly five million. Jeff and Lori came home that night and plunged into the research. Lori read everything she could find and attended local support-group meetings. Most of the advice pointed in one direction: a prescription for amphetamines such as Ritalin. The powerful stimulants (the Food and Drug Administration labels them as Schedule II drugs, the same category as morphine and methamphetamine) have a paradoxical calming effect on the minds of ADHD patients. They're convenient, effective and popular—90 percent of ADHD patients who take them see improvement. Pop a pill; problem solved. Many parents swore by them. Teachers praised them for bringing calm to unruly classrooms.

But the Leibovitzes were reluctant to go that route. They were leery of the side effects, which can include heart palpitations, sleeplessness, dizziness, irritability, headaches and nausea. For the next three years, they opted instead to give Adam and his younger brother plenty of exercise. "We always had a lot of running-around time," Lori says.

Adam became a high-energy kid who was also very bright. By fourth grade, though, the demands of schoolwork began to outrun his ability to keep his ADHD in check. The experience was like having a motion detector wired into his brain. "Every little movement or sound would catch my attention," he says. "If I caught a glimpse of somebody walking past the classroom door, my mind would latch onto that: 'Who's out in the hall? What are they doing out there?'"

His parents worried that he wouldn't keep up. "As he grew older, every year he'd be expected to concentrate a little harder and sit a little longer in his seat," his mother says. "When it came time to do his homework, he'd be rolling around under the table or running into the next room. He'd shout out the answers to us. He always knew the answers. He just couldn't sit still to write them down." When Adam turned 10, his parents decided to try the medication. On Adam's first day on Ritalin, he came home from school and declared it a success. "I felt clearer," he told his parents. "I could sit in class and pay attention." The drug wasn't perfect, though. It was tough to get the dosage right. Sometimes it kept him up at night. Sometimes it made him lose weight, which was worrisome for a skinny kid like Adam. His doctor prescribed Ritalin, then Adderall (a different mixture of amphetamine salts), then some others, then back to Ritalin. "There's a little parental guilt involved in giving your child a Schedule II stimulant," says Jeff Leibovitz. "But the bottom line was: Does the medicine work or not?"

Around the same time, Adam began going on bike rides with his father. Jeff is a Category 2 masters racer. He'd attach a trailer cycle to his bike and tempt Adam to come along on Saturday-morning training rides. "I'd lure him with the promise of fresh doughnuts," Leibovitz remembers. The boy took to riding quickly, almost preternaturally.

There was no way Jeff Leibovitz could have known it then, but that simple weekend ritual would eventually change the boy's life.

For the past 30 years, athletes, coaches, sports psychologists and medical researchers have probed and debated one of the most complex mysteries of the human body: How does exercise affect the brain? Common sense and our own experience tell us it does something. Every parent knows the best way to settle down a hopped-up kid is to take him out to the playground and run the bug juice out of him. A generation ago, teachers and coaches frequently used this approach as well.

This seemed a homespun, intuitive remedy, but in fact there was a scientific basis for it. In 1978, two years before the National Institute of Mental Health (NIMH) recognized ADHD as a condition, W. Mark Shipman, MD, conducted a simple test. Shipman was medical director of the San Diego Center for Children, an institute for psychologically troubled children. Back then, kids at the center were among the few in the United States taking psychostimulants such as Ritalin to calm what was then called hyperactivity. Kids can be naturally impulsive, inattentive, and overactive, but those with ADHD are more so, all the time. (ADHD is an umbrella term that also includes ADD, attention deficit disorder.)

Shipman sent a group of hyperactive kids running for as much as 45 minutes a day, four days a week. An amazing thing happened: The running kids started acting as if they were getting extra doses of medication. After a while, the doctors who monitored the behavior of each child began lowering drug doses for most of the runners. Very few nonrunning participants had their doses reduced. The doctors who were administering the doses didn't know which students were running; the changes in behavior were that clear.

Shipman's study might have led to a boom in physical fitness programs for ADHD-identified kids. It didn't. Instead, just the opposite occurred: Doctors began writing more prescriptions.

At the time of Shipman's study, few parents had heard of Ritalin. By 1988, half a million kids were taking the drug. By 1995 that figure had quadrupled. The United States was using five times as much Ritalin as the rest of the planet combined. "An increase of this magnitude in the use of a single medication," observed pediatrician and Running on Ritalin author Lawrence Diller, MD, "is unprecedented for a drug that is treated as a controlled substance."

It wasn't that Shipman's research was discredited. In fact, at least two other studies conducted in the 1980s confirmed his findings. What happened instead was a societal shift away from time-consuming natural remedies such as exercise and in favor of quick-fix solutions: part of the same cultural sea change that has resulted in the nation's worsening obesity problem.

These changes have reverberated in competitive cycling, a sport filled with athletes whose behavioral traits trend toward the disorder's symptoms; at pro races and masters' events it's not uncommon to hear jokes about cyclists' ADHD-like characteristics. When I ask Jonathan Vaughters, director of the Garmin-Slipstream team, whether he's noticed ADHD-like behavior among any pro riders, he says: "Only the entire peloton."

He is partly serious. "I think a lot of elite cyclists, if properly diagnosed, would probably be shown to have some form of ADHD," he says. Vaughters, a top pro rider in the 1990s, says his son was recently diagnosed with ADHD. "I think he gets it mainly from me," he says. (Vaughters was undiagnosed, but ADHD is often passed from parent to child.)

One of the sport's retired champions, an Olympic gold medalist who asked not to be identified in this story, recently wondered aloud about the effects of Ritalin on the younger generation. In his day, he said, you cycled away your hyperactivity; that was partly how he got into the sport. "I wonder how many kids over the past decade got put on Ritalin instead," he said. "How many potential racers never discovered the sport?"

In other words: How many would-be greats never found cycling because they were medicated?

Adam Leibovitz took Ritalin through his early teens. By the time he entered Indianapolis's Lawrence Central High, though, he'd grown weary of the side effects. He especially disliked what Ritalin users call "robot mode," during which they feel emotionally flatlined.

"I'd take it during the week, go off it on weekends, and then back on again on Monday," Adam recalls. "On Monday I'd be droned out, kind of a zombie. I had no character, no personality. I hated that."

During his sophomore year, Adam asked his parents if he could go off his meds. They decided to let him try. He quit for a few months. He came out of robot mode, but his focus began to ricochet again. As his attention wandered in class, his grades crashed.

By the time school let out in June, Adam was back on Ritalin. During his junior year, he kept a low profile and improved his grades. He wasn't thrilled with the return of the side effects but put up with them for the payoff in the classroom. A shy kid, but not lacking in confidence, Leibovitz didn't hang with the jocks or play a popular team sport. "I didn't have a lot of connections in high school," he says.

Jeff Leibovitz's doughnut lure worked better than he'd imagined. When he was 13, Adam talked his dad into letting him do the TRIRI, a group ride across 300 miles of Indiana countryside, on his own. Around the same time a bike-racing craze swept through the Leibovitzes community, propelled by Guy East, now a professional rider with the Trek-Livestrong team. East, then a teenager, lived nearby, and local kids spotted him whipping past on training rides. Adam and his best friend began entering races.

Adam got really good really fast. He announced himself to the cycling world three years ago, at 15, by finishing third in his first junior national time-trial championship, one place behind 16- year-old phenom Taylor Phinney. Long and lean, Leibovitz had grown into a confident racer with a body that could absorb an uncommon amount of suffering. With his jug ears and big-toothed grin, he could have passed as Michael Phelps's younger brother.

Adam kept racing and winning: the Quad Cities and Tour of St. Louis crits, time trials at St. Louis, Red River Gorge and the U.S. Junior National Championships. "At a certain point he grew beyond my ability to coach him," his father says. Jeff's friend Dean Peterson agreed to work with Adam on a training regimen. Peterson had recently taken over as head coach at Marian University, a small liberal arts school in Indianapolis with one of the nation's top cycling programs.

Peterson's workout schedule introduced concepts like rest weeks and peaking into the young athlete's life. As Adam adapted to the ramped-up program, he began to notice something unusual. He was taking Ritalin on weekdays, but when he trained hard on weekends there seemed to be a carryover effect. On Mondays his mind was calm even before he popped a Ritalin. "I'd experiment with it," he says. "When I was off the meds and rode a lot, I'd feel great. I could concentrate. When I'd take rest weeks I'd be bouncing off the walls."

Halfway through his junior year, with his grades back up, Adam sat down with his parents. Again he said: I've had it. I want to quit the Ritalin. But this time he had a plan. He'd use cycling to manage his ADHD.

Almost immediately, the drug-free experiment was a remarkable success. Adam cruised through the first half of his senior year. He rode nearly every day. During recovery days he'd find other ways to exercise and soothe his brain. Adam's progress was so impressive and his desire to move up to the next level of cycling so great that he cut a deal with school administrators to graduate a semester early. When Peterson offered him a place on the Marian University team, he accepted immediately. This past January, Lori and Jeff Leibovitz helped Adam load up the family car and moved him into the teenage glory of a cinderblock dorm room.

Eventually Adam reached a point where he didn't think much about his condition anymore. When I meet him in Indiana in the spring, he prefers to discuss his goals, like getting to the Olympics, maybe in the time trial or individual pursuit. Or getting a contract with a pro team. Who knows how far he'll make it? Two summers ago he fought off the stomach flu, turned in a sluggish ride, and still won the national junior time-trial championship by more than seven seconds.

He doesn't know how the cycling clears his head, allows him to focus. All he knows is that it works. "Riding," he says, "is my Ritalin."

What is really going on inside Adam Leibovitz's brain?

It probably isn't the endorphins, which mainly affect pain suppression and mood elevation. Researchers now understand that the clearing effect more likely has to do with a different, but similarly mysterious, process centered in the basal ganglia, a part of the brain that plays an important role in movement, coordination, attention, and learning. The most accepted theory about ADHD is that it's largely caused by a deficit of neurotransmitters, which relay signals to and from the basal ganglia. Ritalin works by boosting the concentration of two neurotransmitters in particular: dopamine and norepinephrine. Adam's rigorous race training most likely caused his body to produce the same effect.

"A bout of exercise is like taking a little bit of Prozac and a little bit of Ritalin," says John Ratey, MD, a Harvard Medical School professor who has treated and studied ADHD for more than 20 years. His most recent research is chronicled in his book Spark: The Revolutionary New Science of Exercise and the Brain. The Prozac effect comes from endorphins. The Ritalin effect, Ratey says, has to do with boosting the concentration of neurotransmitters in the basal ganglia. "Regular exercise can raise the baseline levels of both norepinephrine and dopamine," he says, "which are the same neurotransmitters that Ritalin and Adderall go after."

ADHD drugs don't suffer from a lack of critics, but Ratey isn't among them. "I use them for my patients all the time," he says. "They're very useful drugs. But in some cases, if a person does enough exercise then Ritalin becomes a little less vital in the treatment of their condition."

And it's not just any exercise. Some activities are better brain boosters, and cycling is one of the best. David Conant-Norville, MD, a psychiatrist in Beaverton, Oregon, who specializes in adolescents and attention deficit hyperactivity disorder, recently surveyed his colleagues about the best and worst sports for athletes with ADHD. Cycling, swimming, and running are tops. At the bottom are soccer, hockey, and baseball. The best sports demanded constant physical exertion and a suite of technical movements that engaged brain functions dealing with balance, timing, error correction, decision-making and focus.

"ADHD is imperfectly named," says Conant-Norville. "People with the condition don't have a deficit of attention. They have a problem with attention control during boring or mundane tasks. Which is why the intense focus of cycling is great for someone with ADHD. If you're moving in the pack in a cycling race, you're highly focused on other riders around you as well as the road ahead. And you're constantly thinking about strategy, whether to attack or hang back."

John Ratey agrees. "Challenging the brain and body has a greater positive impact than aerobic exercise alone," he says. "We're just starting to see the effects of movement complexity in recent research."

One study in particular caught Ratey's eye. Researchers at a German university last year asked 115 teenage students at an elite sports academy to take a baseline test that measured attention and concentration. Then they were split. One group performed 10 minutes of exercise that required complex, highly coordinated movements. The other did simpler movements at the same level of aerobic activity. The kids took another attention and concentration test. Both groups improved their original results, but the students who performed the complex movements significantly outscored the others. The complex coordination, the researchers concluded, "might lead to a preactivation of parts of the brain which are responsible for mediating functions like attention."

There's another aspect to it as well. Call it gallows focus. "The prospect of the gallows doth wonderfully concentrate the mind," Samuel Johnson once famously wrote, and something similar can be said for exercise that involves a touch of risk. Let your attention drift in the peloton, and you might crash into the rider in front of you. Distraction in the dojo is rewarded with a painful body blow. By contrast, a soccer player who loses his concentration is just a guy standing in a field of grass.

Adam Leibovitz's use of riding as a natural form of Ritalin doesn't surprise Jonathan Vaughters, the Garmin-Slipstream team director. "His experience was my experience," Vaughters says. High school was difficult for him, but his ability to study improved when he started training 25 hours a week. "After a four-hour ride," he says, "I could sit there and concentrate on one topic for an extended amount of time. Without that exercise-induced euphoria, I had a hard time focusing."

Dean Peterson, head coach of the Marian University cycling program, takes a special interest in athletes with ADHD. His son has the disorder, and though Peterson himself was never diagnosed, "from what I've learned over the years I realized that the cycling and cross-country running I did in college helped me manage my own condition," he says.

Over the past year I've spoken with racers across the country, kids and adults, managing their ADHD with the help of cycling. Leibovitz was the only athlete who had quit the drug completely and replaced it with his daily ride. But a number told me they were able to ramp down their Ritalin dosage by mixing a regular cycling regimen into their schedules. It's possible that there is something far bigger going on here.

Peterson believes this to be true. "I think a lot of people are self-medicating," he says, "and may not even know it."

If exercise is so effective, why isn't it more widely used as a treatment?

There's plenty of research to back up the neurotransmitter theory. In 1997, researchers found that treadmill running significantly increased the production of dopamine, that key neurotransmitter, along with norepinephrine, in the brain's attention center in rats. In a later study, German scientists found that intense exercise boosted the human body's production of both dopamine and norepinephrine. In 1999, Michael Wendt, PhD, a researcher at the State University of New York at Buffalo, found marked improvement in ADHD kids who exercised for 40 minutes a day. In 2002, a University of Georgia study reported a promising correlation between exercise and improved focus in children with ADHD.

Each of these studies quietly died on the vine. Beyond a select few ADHD researchers and therapists, exercise is conspicuously absent from most programs and literature related to the disorder. The National Institute of Mental Health's 47-page guide to ADHD makes no mention of it.

Why? Many reasons.

"First, the answer is too simple," says Wendt, the author of the 1999 SUNY study. Exercise improves health: It's not exactly ground-breaking news. There's little incentive for scientists to prove such common wisdom, even if it might be critically helpful to parents and kids with ADHD. "Second, pharmaceutical companies fund a lot of medical research," Wendt says, "and you see no funding for research in this area."

Maybe that's the biggest reason no one has been loudly touting the benefits of exercise: There is no profit in it. Exercise has no drug reps. In 2007, the pharmaceutical industry invested $58.8 billion in research and development. Bike manufacturers don't sponsor medical studies. There's so little money for exercise research, in fact, that Michael Wendt had to finance his ADHD study. It cost him $15,000.

There's something else to consider. During the years when Ritalin prescriptions spread through the nation's classrooms, school districts across America were cutting back on physical education programs and coming under increasing pressure to boost standardized test scores. From 1991 to 1995, the very era when ADHD diagnoses were sky-rocketing, the percentage of high school students enrolled in daily PE classes dropped from 42 percent to 25 percent. For money-strapped school districts, cutting PE became an easy way to save money and devote more time and resources to "teaching to the test."

Given that history, the question posed by the former Olympic medalist seems disturbingly germane. Did we put a generation of potential Tour de France riders on Ritalin instead of giving them bikes?

There's a good chance we did.

That's why what we need now, a number of ADHD researchers say, isn't more research. It's a stronger message—one that bypasses physicians and psychologists and goes straight to kids, teachers and parents.

"There's enough evidence out there that indicates exercise improves focus in children with ADHD," says Spark author Ratey. "My passion now is to get that message into the schools. I want to change the whole concept of PE. Let's make it more based on a fitness model instead of something that revolves around competitive ball games. Make it relevant, get every child involved, and show the benefits to teachers, students and parents."

Ratey spends a lot of his time these days testifying before state legislatures that are considering bills that mandate new physical education programs. Exhibit A are innovative PE programs in Naperville, Illinois, and Titusville, Pennsylvania, where high school students put in an hour of intensive cardio work before class every day. Those programs not only turn out the fittest students in the country, but they're also among the smartest. The correlation between the unique PE programs and improved test scores, says Ratey, "are simply too intriguing to dismiss."

Wendt has applied data from his 1999 study to students in the Wilson Central School District in western New York, where he now serves as superintendent. These programs aren't new. Naperville's program has been going on since 1990 and Titusville's since 1999. But the program has yet to gain much traction in the mainstream. Wendt sends his SUNY study to educators who ask for it. And he's often in touch with peers in Naperville and Titusville, comparing new innovations and pushing the cutting edge.

Adam Leibovitz now represents that cutting edge. Without intending to, the young cyclist is conducting an ongoing experiment that measures the power of the body to improve the mind. When he moved into his dorm last January, Adam brought a quiver of racing bikes and no Ritalin. His intensive training schedule had kept his ADHD in check over the previous fall, but nobody knew whether he'd be able to handle his condition in the same way amid the stepped-up demands of college.

"It's tough enough getting freshmen to manage their classes, training, team meetings and competitions," says coach Peterson. "You throw the ADHD kid into that situation, it becomes more of a challenge."

Through his first semester, Adam kept up a routine: Hit the books, then the bike. His classes were done by noon—"I like to get stuff out of the way early," he says—and then he'd take a short nap.

When he woke up, it was time for his medication. On a typical day Adam would grab his helmet, pull on his jersey, and wheel his bike through the front doors of his dorm. He'd clip in and glide past the ponds and grassy fields on campus, then roll onto 30th Street, near the Indianapolis Motor Speedway, home of the Indy 500. He would ride past cell phone stores and Burger Kings, past auto body shops and tire stores. He'd get in a rhythm by the time he was whizzing past the beltline road where new houses are encroaching on cornfields, and he'd keep going farther still to the place where the city faded and farmland still held its own. This was John Mellencamp country, all corn stubble and mud.

After a bumpy start in his first collegiate races, he would learn to race on a team, and by season's end he would win the conference criterium. Heading into finals week in May, he would feel solidly in control of his life. The first-grader whose parents faced an impossible choice—let him flounder in the system or take a powerful, identity-altering drug—would find a far greater alternative. He would turn out to be a successful college student, a blossoming bicycle racer.

Somewhere out in the vast Indiana flatland, Adam would turn and head home, eventually pulling into the campus cycling center at a little past three in the afternoon. The center, known by team members as "the wattage cottage," is a former storage garage converted into a velo training center. Coach Peterson would usually be there, fixing somebody's brake cable. Adam would park his road bike and join a few teammates pedaling furiously on CompuTrainers.